This invention relates generally to devices for filtering and separating liquids. More particularly, the present invention relates to fuel filters for removing foreign particles and separating water from fuel of the fuel supply system of an internal combustion engine.
The absence of high standards of quality control in diesel fuel supplies dictates that an effective fuel filter be incorporated into the fuel supply system of a diesel engine. It is not uncommon for diesel fuel to have significant quantities of abrasive particles and water. The abrasive particles present the potential for permanent damage to components of the fuel injection pump. The abrasive particles can also adversely affect the performance of the pump by destroying the ability of the fuel injection pump to precisely meter and deliver fuel at high pressures. The presence of water in the diesel fuel supply can cause corrosion of engine components, and during freezing conditions, can result in interruption of the fuel injection system and/or seizure of moving components.
Commonly, fuel filters employ a disposable filter cartridge which is replaced at pre-established intervals of filter usage. There are a wide variety of fuel filter configurations and orientations. In some fuel filter configurations, the disposable cartridge is suspended directly below the base in an inverted disposition which is referred to herein as an inverted fuel filter. While an inverted fuel filter satisfies a number of functional and dimensional constraints for certain applications, a common deficiency of a number of fuel filters, particularly those inverted fuel filters wherein the disposable cartridge is suspended below the base, is that during the replacement process significant quantities of fuel may discharge from the base and spill into the immediate environment. The fuel spillage is undesirable in terms of safety, potential environmental pollution and technican safety and hygiene. The spillage may also result in clean-up and disposal costs.
In U.S. Pat. No. 5,017,285, which is assigned to the assignee of the present invention, one disclosed inverted fuel filter assembly employs a base and a disposable filter cartridge which is suspended directly below the filter base. The cartridge includes a dual stage filter system wherein the fuel flows axially to a primary filter element for removing particulate matter and coalescing water droplets and axially to a second filter stage which functions as a water barrier. The filtered fuel flows generally axially back to the base and exits through an outlet passage in the base. The cartridge is retained on the base by a threaded collar which engages against a roll seam structure at the periphery of the cartridge housing. The base further includes a pair of concentric axial conduits or sleeves which seal with sealing grommets of the disposable cartridge and essentially function as inlet and outlet conduits between the base and the disposable cartridge. In one embodiment, the coalesced water is collected in the bottom of the cartridge and removed via a drain cock.